1. Field of the Invention
This invention relates to a semi-hard magnetic alloy having a composite magnetic property and a method of making the same, and more particularly to a semi-hard magnetic alloy which is a single magnetic alloy but has a composite magnetic property and a method of making such a semi-hard magnetic alloy.
2. Description of the Prior Art
Conventional semi-hard magnetic materials or hard magnetic materials which can be used in the same manner as the semi-hard magnetic materials, have such simple hysteresis loops as shown in FIGS. 1 and 2, respectively. For example, channel switches for an electronic switching system are mainly of the electromagnetic drive type and are roughly divided into a crossbar switch and a switching matrix. The DEX-10 electronic switching system developed by the present applicant employs a small crossbar switch. However, the use of a magnetic self-latching type reed relay with reference to the switching matrix has also been studied and a semi-hard magnetic material has been used therefor.
The magnetic self-latching type switches are classified into a Ferreed type switch having an excitable magnetic core formed of semi-hard magnetic material and a switch having a reed formed of semi-hard magnetic material. These switches utilize the hysteresis loops shown in FIGS. 1 and 2, respectively. Accordingly, they are greatly affected by a change in the driving current when opened and closed, especially when closed. This inevitably introduces complexity in the driving method therefor and requires an accurate control of the driving current.
On the other hand, in the case of using such a hysteresis loop as shown in FIG. 3, which is herein defined as the composite magnetic property (described in detail later on), there exists a stable state of no magnetic flux density, so that a sufficient margin can be provided for current variation. In this case, the opening and closing operations of the switch are achieved based on the smaller loop indicated by the thick line in FIG. 3. It has been found that the use of such a composite magnetic property presents various advantages for the operation of the switch. However, such a composite magnetic property cannot be obtained with any conventional single alloys. For obtaining such a composite magnetic property as shown in FIG. 3, there is known no other method than the mechanical cladding of two alloys of different magnetic properties, that is, two alloys having magnetic properties as given in FIGS. 1 and 2, respectively. Namely, the composite magnetic property of the channel switch for the electronic switching system requires that a smaller coercive force H.sub.c (a) be more than a few dozen oersteds and that a larger coercive force H.sub.c (b) be more than 200 oersteds. However, there has not been obtained as yet a magnetic material which is a single alloy and has such a hysteresis loop as shown in FIG. 3. The present applicants have continued their studies on a method of mechanical cladding of two alloys having different coercive forces. As a result of these studies, it has been found that the two alloys should be compatible with each other in heat treatment and working conditions, that cladding of alloys of different elementary compositions is especially difficult and that the number of conventional semi-hard magnetic material suitable for cladding is very small. Further, according to the studies by the present applicant, the system Fe-Co-Ni-Cr-Cu alloy (hereinafter referred to as the FCNC system alloy) has been developed which has a coercive force of 40 to 350 Oe and is capable of cold working so that, a clad-type composite magnetic core can be obtained which has the hysteresis loop shown in FIG. 3.
The magnetic material having the desired composite magnetic property can be obtained by mechanical cladding. The techniques therefor are disclosed in the Japanese Pat. No. 554,846 (Japanese Patent Publication No. 7836/69) and U.S. Ser. Nos. U.S. Pat. No. 3,422,497, 449,788.
However, such a clad-type magnetic material has the drawbacks of low mass-production and high manufacturing cost, as compared with a single alloy having the same composite magnetic property.
Further, a method for the manufacture of the system Co-V-Mn-Fe magnetic alloy has been developed by Western Electric Co., Inc. The chemical components and properties of this alloy are disclosed in U.S. Ser. Nos. 527,847 and 549,193. However, the composition of the alloy is entirely different from that of the alloy of this invention and the composite hysteresis loop of the alloy is also different from the composite magnetic property of the alloy of this invention. Moreover, the manufacture of the alloy requires a partial annealing for at least 30 seconds and this is achieved under extremely severe conditions in the prior art.